The main goal of this proposal is to test the assumptions made by computational models concerning the operation of specific functions assigned to the hippocampus by developing a set of behavioral paradigms and to examine subregional specificity of the hippocampus. The importance of examining differential contributions of the sub regions of the hippocampus is to understand information flow within the hippocampus, so that it will be possible to determine input-output functions of the hippocampus and understand the contribution that the hippocampus makes to the overall processing of mnemonic information and memory representation. More specifically, the first aim is to develop behavioral paradigms to examine pattern separation processes based on spatial, temporal, and response attributes, to determine whether the dorsal and ventral hippocampus play a role in each of these pattern separation processes, and if so, to analyze subregional specificity (DG, CA1 and CA3) and test predictions made by computational models. The second aim is to develop behavioral paradigms to examine the formation of pattern associations including object-place and odor-place associations that involve non-spatial and spatial associations, odor-object associations that involve non-spatial associations, and odor-delay-object associations that involves non-spatial and temporal information, to determine whether the dorsal and ventral hippocampus play a role in the formation of each of these pattern associations, and if so, to analyze subregional specificity (DG, CA1 and CA3) and test predictions made by computational models. The third aim is to develop behavioral paradigms to examine pattern completion for spatial and temporal information, to determine whether the dorsal and ventral hippocampus play a role in pattern completion for spatial and temporal information, and if so, to analyze subregional specificity (DG, CA1 and CA3) and test predictions made by computational models. It is hoped that this information will be useful in understanding the role of sub regions of the dorsal and ventral hippocampus in processing mnemonic information in humans. This is of special interest since chronic stress appears to produce damage in the CA3 region and hypoxic episodes appear to produce cell loss primarily in the CA1 region.